CHAP 2 Manufacturing Operation

8/7/2019 CHAP 2 Manufacturing Operation

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BMFA 4463

Delivered by :

KhairolAnuar bin Rakiman


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2.1 Product & Production Relationship

2.2 Product Complexity

2.4 Production Concepts

2.5 Cost of manufacturing Operations

2.3 Limitations and Capabilities of a Manufacturing

Plant


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Definition of Manufacturing

Technically

Economically


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Following are considered in determining how to

manufacture the products:

Production quantity

Low, medium, high

Product variety

Soft, hard

Complexity of individual parts

Complexity of the assembled products

Simple assembly

Complicated assembly

Simple part

Complicated part

2.1 Product & Production Relationship


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Product Quantity and Product Variety

Q : Annual production quantity

P: Product variety (total number of different parts / productsproduced in the factory)

So, PQ relationship can be written as

!

!p

j

jf QQ1

fQ

jQ

j

= Total annual production quantity of of all parts

= Annual production quantity of part / product j.

= 1,2,...,P (subscript to identify different parts / products)


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It may be useful to distinguish soft and hard product variety in some cases.

P1: number of distinct products (represents hard variety)

P2: number of different models of a product (represents soft variety)

Therefore

!

!1

1

2

P

j

jPP


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A company specializes in consumer photographic products. It

produces only cameras and projectors. In its camera line it offers 15

different models, and in its projector line it offers 2 models. What is the

totality of product models offered?

P1, P2, P ?

1715222222

2

1

1

1

1

!!!!! !!

PPjPjPPj

P

j

P1=2, P21=2, P22=15

Solution :

Example (2.1 in textbook)


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Product complexity can be defined qualitatively or quantitatively.

2.2 Product o plexity

Quantitatively:

Product Approximate number of

components

Mechanical pencil 10

Bicycle 750

Airplane 1,000,000

Number of processing steps is an indicator of the complexity of a part.

Number of components is an indicator of the complexity of an

assembled product.

Product Approximate number of

processes

washer 1

pump housing 20

6 cylinder engine block 50


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Relation between the level of activity in a manufacturing plant and

complexity.

: numberofparts perproduct

: numberofprocessing steps to makeapart

Assuming

P1 =P2 =P

The products are all assembled and there is no part purchased

Production quantity for each product design is the same (Q).

All products have the same number of components (np).

All components require the same number of processing steps (no).

Total numberofproduct units produced:

Total numberofparts produced:

Total numberof operations performed:

PQQf !

ppf PQnn !

opof nPQnn !

pn

on


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Suppose a company has designed a new product line and is planning to

build a new plant to manufacture this product line. The new line consists

of 100 different product types and for each product type the companywants to produce 10,000 units annually. The products average 1000

components each, and the average number of processing steps

required for each component is 10. All parts will be made in the factory.

Each processing step takes an average of 1 min. Determine:

a) How many products?

b)How many parts?, and

c)How many production operations will be required each year?, and

d)How many workers will be needed for the plant, if it operates one

shift for 250 day/yr?

(1 shift= 8 hr)



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b) The total number of parts

Solution:

a) The total number of products to be produced by the factory

PQQf ! P= 100 (different product types)Q= 10,000 (production quantity for each product type)

Qf= (100)(10,000) = 1,000,000 (products annually)

ppf Qnn !

np= 1000 (each product contains 1000 parts)npf= (1,000,000)(1000) = 1,000,000,000 (parts annually)


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c) The number of distinct production operations

opof nQnn !

nof= (1,000,000,000)(10) = 10,000,000,000 operations annually

d) Total number of workers required

Time required to perform these operations:

Total time = (10,000,000,000 operation/yr)(1 min/operation)(1hr / 60 min)

=166,666,667 hr/yr

Each workers works 8 x 250 hr/yr =2000 hr/yr

Total number of workers is then

w= (166,666,667 hr/yr) / (2000 hr/yr) =83,333 workers !!!


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-A factory practically does not produce everything itself(requires

vendor to supply necessary components)

- Focused factory: plant which concentrates on a limited, concise,

manageable set of products, technologies, volumes, markets.

- Bases defining manufacturing capabilityof a plant;

i)Technological processing capability

e.g. A machine shop cannot forge steel

ii)Physical size and weight of the product

e.g. A plant without heavy-duty cranes may not handle

heavy products

iii)Production capacity (plant capacity)

Definition:Maximum rate of production per period that a plant can

achieve under assumed operating conditions.

e.g. A plant capable of producing 1000 specific products annually

cannot manufacture 2000 pieces of that product per year.

2.3 Li itations and apabilities of a Manufacturing Plant


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2. Production oncepts

Number of products / parts produced per hour (Rp).It is the reciprocal of theproduction time (Tp).

p

pT

R1

!

Production time involves the effects of

setup time (Tsu)and batch size (Q) (in case batch

production),

handling time of the product (Th) and tooling (Tth ),

actual processing time (T

o).


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Production Rate (Rp):

Operation cycle time (Tc)

Time that one work unit spends being processed or assembled.

thhoc TTTT

All are expressed as min/pc.

Batch processing time (Tb)(in case of batch production)

tcsub QTT !

Q

TT bp !

Qin pcs, Tsu in min

Production time in batch production


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Production time in job shop production is same with batch production.

For quantity mass production: (Q is significantly high)

0/ }QTsu

Therefore

p T/1!!

Rc:operation cycle rate of the machine

For flow line mass production: (Q is significantly high again)

The station with the longest operation time: Bottleneck station

)max( orc TTT ccp TRR /1!!

Tr: time to transfer work units between the stations (expressed in min/pc)


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Production Capacity (PC) (Plant Capacity):

Maximum rate of output that a production facility is able to produce under a

given set of assumed operating conditions (shifts and workdays).

pnSHRPC!

PC expressed in units/wk

n: number of work centers in the facilityS: number of shifts per period (expressed in shift/wk)

H: operation time of work center (expressed in hr/shift)

Rp: hourly production rate (units/hr)


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Assumptions in the model:

It is assumed that units are processes uniformly through the

work centers.

All machines are producing 100% of the timeThere is no bottleneck

Solutions to increase the production capacity over

short term

Change the number of shifts

Change the number of work hours per shift

long term

Increase number of work centers ( utilise unused m/c, acquire

new m/c, hire more workers)

Increase production rate by improvements in processing

methods or technology.

Reduce the number of operations by combining or integrating

them (automation)


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The turret lathe section has six machines, all of them assigned to theproduction of the same part. The section operates 10 shift/wk. The

number of hours per shift averages 8. Average production rate of each

machine is 17 unit/hr. Determine the weekly production capacity of the

lathe section.

units/week8160)17)(8)(10)(6( !!! pnSHRP

Solution:


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Utilization (U):

The amount of output of a production facility relative to its capacity.

PCQU /!

Q: Actual quantity produced in a given time (expressed in units/wk)

Utilization can be used for any productive resource (plant, machine,

labor, etc.).

Utilization is generally expressed as a percentage.


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A production machine operates 80 hr/wk (two shifts, 5 days) at full

capacity. Its production rate is 20 units/hr. During a certain week, themachine produced 1000 parts and was idle the remaining time.

a) Determine the production capacity of the machine

b) What was the utilization of the machine during the week under

consideration?

Solution:

a) PC = (80)(20) = 1600 units/wk

b)U= 1000 / 1600= 0.625= 62.5 %

Alternatively, calculate the time spent to produce 1000 units.

H= (1000 units) / (20 units/hr) = 50 hr

U= 50 / 80= 0.625= 62.5 %


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Availability (A):

Measure ofreliability of an equipment.

Commonly defined in terms of MTTR (Mean Time To Repair) and MTBF

( Mean Time Between Failure).

Two approaches in calculation of availability:

MTBF

MTTRMTBFA

MTTRMTBF

MTBFA


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The turret lathe section has six machines, all of them assigned to the

production of the same part. The section operates 10 shift/wk. The

number of hours per shift averages 8. Average production rate of each

machine is 17 unit/hr. Determine the weekly production capacity of the

lathe section, if availability of the machines:A= 90 % and utilization

of the machines: U= 80 %

)( pnSHRUAPC!

units/week5875)]17)(8)(10)(6)[(8.0)(9.0()( !!! pc nSHRUAP

Solution:


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TO BE CONTINUED !

Documents

CHAP 2 Manufacturing Operation